LMSC I made 3 brews today, the first following fairly closely to your regime:
Switch 02 with Drip Assist & Rombouts #4.
#1 - I used 13.8g coffee & 210g water total - 42g with valve closed in centre, at 40s up to 84g, open valve at 1:20 then up to 126g, 2:00 up to 168g, 2:40 up to 210g in centre. Dry bed at 3:20.
Average EY for this coffee is 19.1%, this cup was 19.7%. I noticed the water above the bed was unusually hazy after the last, centre DA pour. Flavour was a little below expectation, a little muddled & dry, filmy mouthfeel.
#2 - I changed up the order of immersion vs percolation - the first 2 pours in the centre of the Drip Assist, then at 1:20 close the valve & pour all the remaining water in the ring, finishing the pour at 2:00. Draw down at 3:20, dry bed at 3:47. EY 19.6% (no difference to the previous cup in real terms).
#3 I still felt this a was a shade silty, so I went a coarser & repeated - Dry bed at 3:44, EY was 18.9%, a cleaner cup and a little sweetness now coming through, I might have gone just a tad too coarse. So maybe dropping a % or two at 400Kruve would be enough.
My reason for immersing at the end of the brew & avoiding the centre of the Drip Assist after the early stages, is that the longer the coffee is wet the more susceptible it is to agitation increasing siltyness.